In general, 2-hydroxypyridine-N-oxides are reported to have antimicrobial activity at a higher concentration than do their 2-thiol counterparts, such as pyrithione, E. Shaw et al., J. Am. Chem. Soc. 72 4362 (1950) and G. Newbold et al., J. Chem. Soc. 1948 1864. The copper salt of 2-hydroxy-5-methoxy-6-methylpyridine-N-oxide has been reported to have, generally, less antimicrobial activity than does either the corresponding iron salt or the ligand parent, W. Barker et al., J. Antibiotics 32 1096 (1979).
Certain copper, iron and other inorganic salts, such as the metal sulfates, have long been fed to young pigs or ruminants as feed additives, see for example U.S. Pat. No. 2,960,406. To the best of our knowledge, organic copper salts have not been used as animal feed supplements in order to increase growth and feed efficiency in monogastric animals.
The parent compounds as well as their many salts, of which only the copper salts are the active ingredients of this invention, are prepared as described in U.S. Pat. Nos. 2,540,218; 2,752,356; 3,773,770; 3,968,118 and 3,972,888. The compounds of these patents are described to have utility as topical antibacterial or antifungal agents, especially as the active ingredients in antidandruff compositions.